“Study nature, not books”
(Louis Agassiz)
Bi 1 Lecture 29
Thursday, June 2, 2005
Evolution 3. Voyages to the Galapagos;
The physiology of Diving Mammals
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Announcements on the Bi 1 Web page:
http://www.its.caltech.edu/~bi1/schedule.html
Review Session takes place here, today, here, 4 - 6 PM.
Sections meet as usual today and tomorrow.
The final exam is posted Thursday (today) 6 PM;
Due Fri 6/10 4:30PM in the Bi 1 Closet
Graduating seniors: papers are due today 5 PM in the Bi 1 Closet
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Acknowledgements
“It takes a village to teach Bi 1 at Caltech”
TAs, both grads and undergrads
Professional staff:
Dr. Jane Mendel, Head TA: Sections and grading
Patricia Mindorff, communications
David Mathog, Molecular Graphics
Eric Slimko, Webmaster
Biology Electronics shop computer support:
Mike Walsh and Pam Fong
Guest lecturers:
Robert Freedman
David Anderson
Cameo appearances from Biology Faculty
Advice from other Core Curriculum Resources
You, the students
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The Voyage of the HMS Beagle 1831-1836
Charles Darwin (born 1809), unpaid naturalist
Azores
Cape
Verde
Islands
Cocos Islands
Tahiti
Galapagos
Islands
35 day visit
Canary Isles
Bahia
Rio de
Janeiro
Valparaiso
Montevideo
Cape of Good Hope
King George
Sound
Tasmania
Falkland Islands
Cape Horn
New
Zealand
journey out
journey home
4
Equator
Punta
Espinoza
Age of the
archipelago:
~ 1 million yr
British Admiralty chart of the Galapagos Islands, based on the Beagle’s observations 5
Darwin’s Finches
(5 genera,
including Geospizia)
• 13 Species, each endemic to the islands
• El Nino poses a survival challenge
• Highly specialized beaks
• Observable evolution in beak size
• Distinctive feeding habits
cactus finch
ground finch
tree finch
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The voyage of the Beagle convinced Darwin that
1.
Members of the same species often change slightly in
appearance after becoming geographically isolated from each other
2.
Organisms living on oceanic islands often resemble
organisms found living on a close mainland
3.
Factors other than or in addition to climate play a role in the
development of plant and animal diversity
4.
Organisms of the past and present are related to one another
(but there are no fossils in the Galapagos)
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"The distribution of the tenants of this archipelago would not be nearly so
wonderful, if, for instance, one island had a mocking-thrush, and a second
island some other quite distinct genus.... But it is the circumstance, that
several of the islands possess their own species of tortoise, mockingthrush, finches and numerous plants, these species having the same
general habits, occupying analogous situations, and obviously filling the
same place in the natural economy of this archipelago, that strikes me
with wonder...."
Darwin, The Voyage of the Beagle
http://www.literature.org/authors/darwin-charles/the-voyage-of-the-beagle/chapter-17.html
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Finch family tree based on a 660-nt sequence
Molecular Biology and Evolution 18:299-311 (2001)
Darwin’s
Galapagos finches
.01 change per position
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Red-Footed Booby
(Ben Lester)
Blue-Footed Booby
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Masked booby
A recently discovered a behavior, called siblicide, occurs among booby chicks.
The larger chick always kills the younger chick, sometimes aided by the parents.
Scholars debate the selective advantage of such behavior.
Perhaps the parents succeed better by insuring the survival of at least one chick.
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Male Frigate Bird Displaying
no oil on feathers
cannot land on water
steals other birds’ fish
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Galapagos Waved Albatrosses in Courtship
2 m wingspan
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Video of Galapagos Waved Albatrosses in Courtship
15
photo by
Ben Lester
Female Albatross on the nest
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photo by
Ben Lester
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The Galapagos tortoises reach sexual maturity at the age of 40
and have clutches of 2 - 26 eggs.
Eggs hatch at 85 -180 d.
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Galapagos Penguins
World’s Northernmost population of penguins.
After "El Nino" in 1983 the population decreased from 12,000 to just 2,000 birds.
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Marine Iguanas
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Marine Iguana feeding
Marine iguanas feed once a day.
The mature lizards swim out through the tidepools to dive to the
bottom for algae; smaller iguanas feed off the rocks in the tidal zone.
An iguana may lose up to 10 degrees C of body temperature on these
feeding missions. Because they are cold-blooded ("ectothermic") ,
iguanas must bask on the hot lava rocks throughout the day until they
raise their internal temperature.
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The increased rainfall that accompanies El Niño results in greater food availability for
most terrestrial organisms in the Galápagos, but marine life generally suffers from the
higher water temperature, which decreases the amount of dissolved oxygen.
Green and red algal species, which are the marine iguanas' preferred food,
disappear and are replaced in intertidal areas by brown algae which iguanas find
hard to digest. Up to 90% of marine iguana populations on islands can die of
starvation as a result of these environmental changes.
During a recent El Niño event (1997–98), larger individuals of the two island
populations shrank more than smaller individuals. The scale of the shrinkage — up
to 20% of body length — means that it cannot simply be explained by decreases in
cartilage and connective tissue, which together make up only 10% of total body
length. Apparently bone absorption accounts for much of the reduction.
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The fight against salt
at Punta Espinoza:
marine iguanas
cormorants
sea lions
Marine Iguana
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salt crystals
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Flightless Cormorant drying its feathers at Punta Espinoza
large flightless birds are common on islands, e.g. kiwi (New Zealand)
extinct:
Great auk (north Atlantic), dodo (Mauritius),
solitaire (Reunion, Rodrigues), moa (New Zealand)
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California Sea Lions
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short-eared owl (flies)
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Flamingos in a salt marsh
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Pelicans
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Land iguana
(Conolophus sp)
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Lava lizard doing pushups
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Territorial iguana chase
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Sally Lightfoot crab
Resembles black crab of Hawaii’s Big Island
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stingless bee
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Pinnacle Rock on Bartolome:
Excellent diving, lots of marine life
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The Physiology of Diving
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Emperor penguins
Aptenodytes forsteri
550 m
22 min
typical: 2-10 min, 50-500 m
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Elephant seal
Mirounga leonina
1600 m
120 min
typical: 20-30 min, 200-800 m
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Weddell seal
Leptonychotes weddellii
> 600 m
82 min
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Bottlenose dolphin
Tursiops truncutus
210 m
5 min
typical 30 m, 120 s
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Blue whale
Balaenoptera musculus
300 m
50 min
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Sperm whale
Physeter macrocephalus
3000 m
90 min
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In metabolism, electrons move around inside cells until they reach oxygen,
which has the highest electron affinity of the biological elements
Little Alberts 2-7
© Garland
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Diving mammals must store oxygen in order to conduct aerobic metabolism
Emperor penguin
Baikal seal
Weddell seal
In the absence of oxygen,
glucose 
pyruvate and lactic acid.
~ 2 moles of ADP are converted
to ATP.
In the presence of oxygen,
glucose + O2  H20 + CO2.
~ 24 moles of ADP are converted to ATP
enzymes and carriers transfer 40%
of the bond energy to high-energy
phosphate bonds, in small steps.
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Diving mammals have much higher:
blood volume
hemoglobin concentration
and especially myoglobin
two oxygen-carrying heme proteins
than other mammals.
More than 80% of the oxygen is in the blood and muscle.
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Diving mammals have much higher:
blood volume
hemoglobin concentration
and especially myoglobin
two oxygen-carrying heme proteins
than other mammals.
More than 80% of the oxygen is in the blood and muscle.
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Crittercam (UC Santa Cruz)
35 cm
detachable
CCD
lens camera
900 nm LEDs
batteries
and
8 mm
tape recorder computer
float
transmitter
Ti or Al
housing
fins
Audio channels
(1) accelerometer
(2) microphone
Transducers for pressure, water speed, and compass bearing are sampled once per
second, and the data are stored on a PCMCIA card. A separate housing (17 cm long
and 5.5 cm in diameter) for the gimbaled flux-gate compass is positioned behind the
main housing and connected to it with a cable.
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Diving mammals glide much of the time
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Diving mammals save ~ 28% of their energy by gliding
(plexiglas dome)
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Bottlenose dolphins save energy by slowing their heart rate during a dive
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Pressure effects on air gases
10 m = 1 bar
Sport diving is limited to ~ 40 m
1.
The bends: N2 bubbles form in the blood
2.
Nitrogen narcosis
3.
Oxygen toxicity
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Tanks
200 bar
Regulators
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Diving mammals don’t get the bends: adaptations to pressure
“Lungs are a liability for deep divers because, in contrast to muscle and blood,
they are a better nitrogen store than oxygen store.”
a. flexible chest;
b. no collagen in the
smallest branches
“The early occurrence of lung collapse in
seals makes the lung almost useless as
an O2 store, whereas it limits N2
absorption during the dive.”
Some compressed air
remains in the windpipes,
but a collagen lining
prevents absorption by the
blood
complete peripheral collapse
at 20-50 m
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Other effects of water’s high density
1.
Heat capacity and heat conduction
Diving mammals solve this problem with blubber.
Scuba divers use exposure suits (wet suit, dry suit).
Both of these materials compress at depth, increasing the
animal’s density and providing negative buoyancy.
2.
Greater index of refraction
3.
Greater speed of sound
4.
Greater light absorption
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2. Objects look larger to a diver (Phys 2a)
apparent
object
real
object
q’
q’
water
n’ ~ 1.3
q
air in mask
n=1
q
nsinq = n’sinq’
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3. A diver cannot judge sound direction
delay between the two ears
~ 7 sin q ms
(can be determined
to within ~ 10 ms)
q
Sound travels
3-4 times faster in water
20 cm
0.2 m/(300 m/s)
~ 7 ms
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4. Objects look blue to a diver
a few m of water absorbs
long wavelengths
shorter wavelengths
penetrate further
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A Summary of Adaptations in Diving Mammals
1. Compressible lungs: decrease buoyancy, decrease bends
2. High myoglobin concentration
3. Blubber
4. “Intermittent locomotion” = gliding
6. Decreased heart rate decreases heat flow
5. Wave riding and jumping
6. Countercurrent cooling devices for testes
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Darwin, The Voyage of the Beagle
Darwin, The Origin of Species
Michael Jackson, Galapagos, University of Calgary Press, 1994
Jonathan Weiner, The Beak of the Finch: a Story of Evolution in our Time,
Knopf, 1995
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